How do tuxedo fittings usually go?
Hardly. They will measure you with a measuring tape, and perhaps have you try on a jacket, and shoes if you don’t know your size. It’s really quite painless. In the event that you do have to change into something else (a dress shirt, for example, to make the jacket fit more accurately) you would do so in a changing room. Don’t worry about it. Think about more important things, like how only an idiot would wear a long tie instead of a bow tie with his tuxedo.